History Of Astro

The History of

Astronomy

Mayan Calendar 4000 B.C.

• Calendar based on the motion of the moon and the seasons

• Calendar was developed to help manage crop growth and to determine when to hold rituals

Eratosthenes of Cyrene

• 240 B.C.• Measures the

circumference of the Earth

• THE EARTH IS ROUND!!!

Stonehenge 2000 B.C.

Ptolemy 140 A.D.

• Geocentric Universe• The Earth is at the

center of the Universe• Orbits and retrograde

motion of the planets were explained through epicycles

Ptolemy’s Epicycles

Julius Caesar 45 B.C.

• The Julian calendar• First widely adopted

SOLAR calendar • Based on observations

by Greek astronomer Sosigenes

Copernicus 1543• publishes De

Revolutionibus Orbium Coelestium

• Mathematical evidence for a Heliocentric Universe

• He proposed the idea of a rotating Earth that revolved around the Sun

• A simple solution to the apparent motion of the heavens and retrograde motion of the planets.

Copernicus cont…

• On April 12, 1615, Cardinal Roberto Bellarmine, the leading Catholic theologian, wrote an often-quoted letter to Paolo Antonio Foscarini, a Carmelite monk from Naples who had published a tract defending the Copernican system. Bellarmine’s letter, which was obviously intended as much for Galileo as for Foscarini, opened on a conciliatory note: "For to say that assuming the earth moves and the sun stands still saves all the appearances better than eccentrics and epicycles is to speak well. . . . But to affirm that the sun is really fixed in the center of the heavens and that the earth revolves very swiftly around the sun is a dangerous thing, not only irritating the theologians and philosophers, but by injuring our holy faith and making the sacred scripture false"[1].

Tycho Brahe• DATA, DATA,DATA• “Psycho Tycho” • Tycho was an eccentric

mathematician who worked for the Church. He would lock himself away for days at a time and stare at the stars

• He compiled volumes and volumes of data of the position on hundreds of celestial bodies

• He never allowed a single volume out of his room.

Johannes Kepler (1571-1630)

• Kepler was Brahe’s main assistant when Brahe died

• He used Brahe’s data to create the 3 Laws of planetary motion

• Kepler was the first strong supporter of Copernicus

Kepler’s 3 Laws

• LAW 1: The orbit of a planet/comet about the Sun is an ellipse with the Sun's center of mass at one focus This is the equation for an ellipse:

X2 + Y2 = 1

A2 B2

Kepler’s 3 Laws

• LAW 2: A line joining a planet/comet and the Sun sweeps out equal areas in equal intervals of time

•http://home.cvc.org/science/kepler.gif

Kepler’s 3 Laws

• LAW 3: The squares of the periods of the planets are proportional to the cubes of their semimajor axes:

Planet P (yr) a (AU) T2 R3

Mercury 0.24 0.39 0.06 0.06

Venus 0.62 0.72 0.39 0.37

Earth 1.00 1.00 1.00 1.00

Mars 1.88 1.52 3.53 3.51

Jupiter 11.9 5.20 142 141

Saturn 29.5 9.54 870 868

•Example - If a is measured in astronomical units (AU = semi-major axis of Earth's orbit) and sidereal period in years (Earth's sidereal period), then the constant k in mathematical expression for Kepler's third law is equal to 1, and the mathematical relation becomes T2 = R3

Galileo Galilei (1564-1642)

• “Invented”(Dutch) the refractor telescope

• Discovered mountains on the moon

• 4 moons of Jupiter• Condemned by the Church

and put under house arrest

• The Catholic Church publicly apologized in 1992…350yrs after his death!

Gregorian Calender October 1582

• Rome's  calendar was off by 11 days. So they decided to subtract the extra days. Thus October 4th, 1582, actually became October 15, 1582. This is the calendar that we use today in the Western world. The Greeks and Russians still use the old Julian calendar. That is why they have a different date for Easter even though it is not at the time of the full moon.

Sir Isaac Newton (*1642-1727)

• Newtonian Telescope (reflector)

• Law of Gravity

Gravity(N)=M1*M2

D• Law of Inertia• 2nd Law F=Ma• 3rd Law Every action has

an equal and opposite reaction

Edmund Halley (1656-1742)

• After studying the comets of 1456, 1531, 1607, and 1682

• He noted that the periods and orbits of the comets were the same…using Kepler’s 3rd Law. He predicted the next time this comet would be seen. It was later named …

Halley’s Comet

Albert Einstein (1879-1955)

• Revolutionized the world of physics

• His theories of relativity and equivalence would be support after vigorous testing

Stephen Hawking (1942- )

• Quantum theory of Gravity

• Theories support the inflationary universe

• Black Holes the size of elementary particles

• A Brief History of Time